1. Field of the Invention
The present invention relates to a fluorescent X-ray analyzer and method of determining the concentration of elements in a sample with high reliability in a short period of time.
2. Description of Related Art
X-ray analyzers and qualitative analytical procedures for accurately analyzing a sample containing an element that is capable of generating fluorescent X-rays when impacted by primary X-rays have been successfully used. U.S. Pat. No. 5,418,826 is an example of an analytical method. An example of a conventional analytical method is set forth in FIG. 6, wherein the procedures for quantitatively determining the concentration of elements contained in a sample are disclosed. Referring to FIG. 6 in step 301, a measurement (t) is set, and a measuring cycle is started in step 302. Subsequently, a measurement is conducted in step 303 and the measurement cycle is completed after a lapse of time t in step 304. A calculation of the concentration of the elements and an accuracy, based on a standard deviation of calculated results, is performed in step 305. Finally, the results of the concentrations and their accuracy are displayed, for example, on an LCD screen or printed by the use of a printer in step 306. Frequently this method repeats the calculation procedures several times, for example, 2 to 10 times. Alternatively, the measurement can be conducted at one time followed by an estimation from a counting of X-rays to verify the accuracy of the calculated results of the concentrations.
The conventional analytical methods employed, however, have had the following disadvantages:
(1) The calculated results of concentrations are obtained only after expiration of the time t which was set as the measuring time period, as conducted in step 301, so that the analytical method is inferior in increasing the time for measurements.
(2) In addition, the accuracy of calculated results of concentrations is obtained merely after the time t is set, so that, in order to measure the concentrations of the elements contained in the sample accurately, a measuring time must be conservatively set.
The above-described disadvantages will be below-described with reference to one example. In the measurement of sulfur (S) (hereinafter referred to as a concentration of sulfur) contained in fuel oils, such as heavy oil, by the use of a conventional fluorescent X-ray analytical method of this type, the measuring time t as shown in step 301 is set at a first stage of measurement. In order to conduct the measurement accurately, it has been necessary to measure whether the concentration of sulfur contained in the heavy fuel oil sample is the standard value of (1 wt %) or less, which has required a long measuring time t such as 600 seconds. However, although the calculated result of the concentration of sulfur in this sample was found to be 0.9 wt %, it has been found in the present invention that whether this calculated result of concentration is the standard value or less or whether it is not equal to such a value can be sufficiently judged by measuring for only 10 seconds without expressly using the full measuring time t to an extent of 600 seconds.
Accordingly, the industry is still looking for an improved fluorescent X-ray qualitative analytical system and method for determining the concentration of an element in a sample in an efficient manner.